1. Technical Field
This invention relates to a synthetic resin retainer mounted mainly in ball bearings that are rotated at high speed, and a ball bearing in which such a synthetic retainer is used.
2. Background Art
JP patent publication 2003-343571A discloses a synthetic resin retainer for use in a ball bearing that is rotated at high speed.
The synthetic resin retainer disclosed in JP patent publication 2003-343571A comprises two annular members made of synthetic resin and each having a plurality of hemispherical pockets formed in one side thereof so as to partially receive balls therein, and joint portions each provided between adjacent pockets. Each joint portion is formed with an engaging hole and an engaging claw configured to be engaged in the corresponding engaging hole formed in the other annular member to join the annular members together.
Since the two annular members forming such a conventional retainer are formed of synthetic resin, it is difficult to provide an end product having intended dimensions due to shrinkage and deformation after forming. In view of this difficulty and for easy assembly of the retainer, conventional retainers of this type have their engaging claws designed such that they have a width in the diametrical direction of the retainers that is smaller than the width of the engaging holes in the diametrical direction of the retainers.
Thus, when the two annular members are joined together into a retainer by engaging the engaging claws in the engaging holes, gaps form between the engaging claws and the engaging holes in the diametrical direction of the retainer. With such a retainer mounted in a bearing, when the ball bearing rotates, the plurality balls rotate alternately faster and slower than the retainer, thus applying loads to the retainer. This causes elastic deformation of the annular members by amounts corresponding to the gaps between the engaging claws and the engaging holes in the diametrical direction of the retainer, which results in sliding movement between the engaging holes and engaging claws. Thus, the engaging portions of the engaging claws tend to become worn, which in turn causes the following problems.
Due to wear of the portions of the engaging claws that are in engagement with the engaging holes, the annular members loosen, thus increasing the width of the retainer as well as the diameter of the pockets. This in turn increases the axial and diametrical movements of the retainer. As a result, the annular members forming the retainer become more likely to interfere with, i.e. come into frictional contact with, other parts of the bearing, such as the outer ring, inner ring and bearing seals, thus increasing the bearing temperature due to heat buildup resulting from frictional contact. This leads to deterioration of the lubricating grease in the bearing. Also, wear powder produced from such frictional contact portions tends to get into contact portions between the balls and the raceways of the inner and outer ring. This could shorten the lifespan of the bearing or cause the bearing to produce noise.